Soild Revolutions, surface area etc.

[MathWarrior]

In calculus when you learn solids of revolution in relation to surface area or volume is there any specific uses that someone could enlighten me on in which this would be used. The only example I can think of is a lathe, and calculating its mass using the volume. Other then that I haven't seen any true uses for this. So has anyone found a particular use they'd like to share?

 

[Unrest]

It helps show how integration can be used. Once you understand volumes of revolution it's easier to create your own integrals for, say, the mass of a non-uniformly dense spherical object, or the rotational inertia of a disk-shaped flywheel whose thickness varies with radius. Or just integrating other quantities over 3D space, like say fields in physics.

I suppose you could also use it to find the volume of a pressure vessel with a dished end. Those things are usually defined by piecewise functions which would be easy to integrate.